Japanese Unexamined Patent Application Publication No. 11-147473 describes a steering effort support device that can reduce the steering effort for a driver in a curve road and accurately instruct a driver to perform a steering operation along a curve road by applying a suitable steering effort control torque in response to a steering effort support request ([0009], Abstract).
In this steering effort support device (Abstract), a curvature calculator 4A calculates the curvature ρ of a drive lane ahead of a vehicle 1, and a vehicle velocity detector 32 detects a velocity V of the vehicle 1. A control torque calculator 5 calculates steering effort control torque Tg based on the curvature ρ of the drive lane calculated by the curvature calculator 4A and the velocity V of the vehicle 1 detected by the vehicle velocity detector 32. A controller 6 controls a steering actuator 21 so that the steering effort control torque Tg calculated by the control torque calculator 5 will be generated in a direction to assist the vehicle 1 in turning along the curve.
In calculating the steering effort control torque Tg, the lateral acceleration G is also calculated based on the curvature ρ of the drive lane and the velocity V of the vehicle 1 ([0048], FIGS. 6 and 7). Additionally, considering a case in which a drive lane is not recognized based on image information, a lateral acceleration sensor may also be used for detecting the lateral acceleration ([0053]).